I'd agree with NJwirenut...light coloured plastics deteriorate very quickly under UV (sun or flouro light). You can see the plastic has become brittle and cracked where the wire has been bent back out of its original shape.

How old is it? I haven't seen a 100 amp service on a residence in decades, even old ones. I would guess that it's at least 40 years old, correct? If so, I would imagine that anything exposed to the sun for that long would fade, just like our skin!

Between the PoCo drop, going into the weatherhead? Probably installed by a contractor, then.

I'm not sure we're looking at sun damage. I've seen many an instance of the colors fading, while the base plastic remained just fine.

Out here, there was a firm selling wire that was not UV resistant at all; the PoCo ran miles and miles of it. Now, the PoCo get to replace it all - and the maker is nowhere to be found. Here is a pic of the substandard wire:

I don't see that sort of 'alligator skin' damage to the insulation. Could the insulation have been damaged by something rubbing against it?

EV607797, The service was a Zinsco "all-in-one" with some (about 50%) GTE/Sylvania breakers in it. Zinsco was sold to GTE/Sylvania in 1973. I don't know any more than that.There's lots of 100 Amp services here on the West Coast.

Reno,The alligator skin is there alright, but it goes all the way around the red and the white. The black has it to a lesser degree, and it doesn't show any effect to the area not in direct sunlight. There is an old pepper tree overhanging the roof.

I installed some 4/0 AL SEU cable like that about seven years ago for a customer who wanted to supply her own materials. She got it from Home Depot. It had one black conductor and one red conductor. For residential single-phase, WHY? After a few months in the sun, at the weather head, the black conductor looked fine but the red conductor had turned pink. About a year later, I saw it again and by then, it had turned a pale pinkish-white. I can just imagine what it looks like now. I know the code says that SE cables don’t need to be rated UV resistant when exposed for connection at the service drop, but why even make crap like that?

EV607797, The service was a Zinsco "all-in-one" with some (about 50%) GTE/Sylvania breakers in it. Zinsco was sold to GTE/Sylvania in 1973. I don't know any more than that.There's lots of 100 Amp services here on the West Coast.

Zinsco......Thank goodness that cancer didn't spread much to the east coast! They existed here, but not for long. No offense intended about the 100A services, probably due to lower heating loads in your parts. We do see them here, but rarely on a residence that's less than 40 years old.

I will say that I've seen some THHN/THWN that was either black or white as far as the base insulation color and the nylon outer covering provided the actual coloring. I remember that red was usually white underneath the nylon. I think that I saw blue and green done the same way. I guess that manufacturers saved money by NOT adding pigment to the base conductor insulation and just coloring it on the outside.

There was a time when you could actually specify THHN or THWN, but not anymore. All you will ever see today is a combo. Maybe what you saw was THHN from the 1960's?

Sunlight will do quite a job on anything. The outer nylon jacket cracks, exposing the underlying base color.

I installed some 4/0 AL SEU cable like that about seven years ago for a customer who wanted to supply her own materials. She got it from Home Depot. It had one black conductor and one red conductor. For residential single-phase, WHY? After a few months in the sun, at the weather head, the black conductor looked fine but the red conductor had turned pink. About a year later, I saw it again and by then, it had turned a pale pinkish-white. I can just imagine what it looks like now. I know the code says that SE cables don’t need to be rated UV resistant when exposed for connection at the service drop, but why even make crap like that?

I agree about the black/red question. In single phase, what difference does it make? If phasing really mattered, shouldn't it be a black and a red for one job, a red and a blue for another and a blue and a black for the third? It's just silly. Aside from troubleshooting purposes, I don't see the need to color the legs.

I'm sure that the red conductor you saw was just painted onto a black XHHW conductor. I remember it....It looked like someone was just standing there with a red paint brush as the black cable came out of the assembly line. Nowadays, it's just a red racing stripe at best. I am simply delighted with the new 6/3 Romex where all conductors are black with colored stripes. I know that the manufacturers are doing this to save money, but man those stripes are hard to see when terminating on a surface-mount range receptacle where you don't have a lot of slack.

Then on the other hand, while a certain manufacturer thinks that #6 Romex and above can use racing stripes on black, they are marketing colored 4/0+ in all colors? I must be missing something.